Iceberg ploughmarks on Rockall Bank, NE Atlantic

Abstract

The largest icebergs delivered at present to the North Atlantic are calved primarily from fast-flowing outlet glaciers of the Greenland Ice Sheet. However, recent studies of palaeo-iceberg ploughmarks across the North Atlantic reveal multiple sources of gigantic icebergs with keels as deep as 1 km that were calved from former circum-North Atlantic ice-sheet margins, including the Greenland and Laurentide ice sheets, as well as Iceland, the Faroe Islands and Svalbard. Rockall Bank, between Europe, Greenland and North America (Fig. 1a, e), received icebergs from multiple sources during past glacial maxima, as revealed by seafloor imagery showing its extensively ploughed surface (Sacchetti et al. 2012). Fig. 1. Multibeam shaded-relief bathymetry of iceberg ploughmarks on Rockall Bank. ( a ) Ploughmarks on the southern Rockall Bank. Rose diagrams show ploughmark directions for the three sides of the bank shown. ( b ) Image from the western side of Rockall Bank. Numerous ploughmarks of variable width and length cross-cut each other and show different degrees of preservation. Sparse grounding pits are also visible. ( c ) Different types of ploughmarks are observed in the western part of Rockall Bank, from long and wide isolated furrows (up to 800 m wide) to a mix of smaller furrows with different amounts of cross-cutting. ( d ) A mix …